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14 4 F E R N S OF NOR'I'H AMER ICA .
outside of these areoles the veinlets run obliquely to the margin,
as in the sterile pinnæ.^ A special linc-like receptacle is
formed on the under surface nearly following the outer boundary
of these areoles, but not exactly coinciding with it. This
receptacle bears abundant sporangia, and outside of them a long
and narrow involucre, which is free along its inner margin, and
at first covers the sporangia, but is pushed back as they mature,
and is at length reflcxed.
This band of sporangia each side of the midrib, covered at
first by a special involucre which is remote from the margin of
the frond, is characteristic of the genus Blechnum. The venation
of the fertile pinnæ varies somewhat in the different species.
About twenty species arc now recognized ; more than half of
tliem are natives of tropical or south-temperate America; and the
rest are found in the East Indies, in Africa, in Australia, or in
Polynesia. One species has often simple lanceolate fronds ; a
few have pinnatifid fronds ; several, like our plant, have pinnate
fronds ; and one has very much elongated bipinnate fronds, with
the climbing and twining habit of a Lygodium. This species,
B. volubile (Kaulfuss), occurs in the West Indies and South
America, and has been considered the type of a separate genus
{Salpichloend) by John Smith and Presl.
The genus Blechnum, with Lomaria, Sadleria, of the Pla-
waiian Islands, Woodwardia and Doodya, compose the tribe
Blechnece or Lomariece, a group which is intermediate between
* T o see these areoles, remove the sporangia and the involucre from a fertile
pinna, and view it with a strong lens b y transmitted light. T h e areoles may also be
seen faintly from the upper surface by reflected light.
IT *
FERNS OF NORTH AMERICA. 145
Pterideæ and Asplenieoe, and is characterized by having more or
less elongated sori parallel to the costa, cither near it or remote
from it, but not properly marginal, and provided with a special
involucre attached to the receptacle outside the sorus, and opening
along the edge nearest the costa. Lomaria approaches
Pteridece with inconvenient closeness, and is referred to that
group by Mr. Baker; while by Mettenius it was united with
Blechnum, and put in his tribe Asplenieæ.
Sadleria is probably peculiar to the Hawaiian Islands. The
plants have erect trunks a few feet high, and large coriaceous
fronds, with numerous elongated pinnatifid pinnæ. The sori are
arranged like those of Blechnum along each side of the midveins
of the segments, and there are narrow paracostal areoles like
those of Blechnum serrulahnn, but the indusium is more coriaceous
and persistent. The number of species is uncertain : there
are at least two, and may be three or four ; but it is impossible
to decide without better and ampler specimens than have as yet
been sent from those islands. Woodwardia is represented in the
United States by three species; and Doodia consists of a few
species with small-sized fronds, and fructification much like that
of Woodwardia.
The Florida Blechnum was discovered first by Michaux
upon the banks of the stream Aisa-hatcha. It was not collected
again for many years until rediscovered somewhere in
East Florida by Mr. S. B. Buckley. It has since been found by
many travellers, and is now well known in. herbaria. Mr. Merrill
has had it in successful cultivation at Cambridgeport for some
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